When It Comes To Cannabis Studies, Trust No One

It feels like a new cannabis study comes out every week, nowadays, alternatively praising cannabis as the cure for everything or warning us that it’s going to cause a pancreatic cancer epidemic in dogs. And even as someone who literally works full-time to keep track of it all, it often feels like being a dog at a tennis match. By far the most frustrating thing about the spotty science, however, is seeing how willing some people are to massage cannabis studies for their own ends.

A recent piece in the Washington Post, “Pot Holes,” illustrates this nicely. “Legalizing pot is fine,” its subhead cautions. “But don’t ignore the science on its dangers.” Those dangers include claims that adolescent cannabis use corrupts the brain, makes teens drop out of school, and—a la Reefer Madness—drives them to suicide. There’s also, of course, the requisite reminder that cannabis is a gateway drug (it’s not).

The arguments she uses against legalization appear, as you read the piece, science-based. Its author, Judith Grisel, is a neuroscientist at a respected university and a former cannabis user herself. This being the Washington Post, not some nutty prohibitionist blog, the cannabis studies she cites are from reputable sources (depending on how you feel about NIDA) and they’re all linked in the text.

But do they prove the author’s argument that cannabis is a serious and imminent public health threat to children, one we’re tumbling into blindly? Not really. The thing is, scientific studies are extremely difficult to trust, in general, and even more so when it comes to cannabis studies. 

“Because the range and quality of cannabis studies—and just the variability of the data collection techniques—whatever you want, you can find support for it,” says Dr. Josh Kaplan, a postdoc fellow in neuroscience at the University of Washington who specializes in medical cannabis research.

A lot of earlier cannabis studies, he notes, were as simple as asking people if they smoked weed and what it felt like. Then, he says, “It moved to this, I would say, hyper-salient assessment of cannabis’ effects. Meaning, instead of looking at normal human use patterns, let’s hit the brain with a ton of just THC. Which we know is not normal human use patterns, because there are other cannabinoids [in cannabis] that are present, some that counteract THC’s effect.”

One of the biggest problems with cannabis studies, Kaplan thinks, is that they aren’t usually using the actual cannabis that people smoke. Cannabis’ effects aren’t due to one single molecule, he points out, and blasting CB1 receptors with a single synthetic cannabinoid does not tell us much about the real experience of using cannabis. 

Joelle Puccio, a nurse and researcher who sits on the board of the People’s Harm Reduction Alliance, points out that cannabis studies also often fail to sufficiently control for things like socioeconomic status.

“With cannabis, when you look at poor people who have had generations of systemic oppression based on race or poverty or whatever, they do poorly,” she says. “When we look at middle-class people who maybe haven’t had much systemic oppression or racism, they do okay. And then when we look at rich people, they do great! It’s not really cannabis that we’re looking at.”

Kaplan agrees, adding that subjects in cannabis studies are often using drugs other than just cannabis, frequently including nicotine and alcohol.

“That’s always something to consider,” he says. “Is it cannabis, is it the combination of nicotine with THC? That does seem to have harmful effects. It’s hard to isolate the impact of cannabis alone on brain development.”

These criticisms could apply to a number of the supporting cannabis studies in “Pot Holes”—this rat study Grisel cites involves the exact CB1 receptor blasting Kaplan described. Several of the cannabis studies cited in “Pot Holes” are also from either the National Institute on Drug Abuse (NIDA), known for its anti-cannabis bias, or other institutions whose sole mission is to study drugs from the perspective of abuse. But the issue of bias is by no means limited to anti-cannabis op-eds.

“People want to sell articles, and they want to get clicks and headlines,” Puccio points out. However, she notes, the problem is widespread. “That’s not unique to the regular media either. People who are trying to get tenure or trying to get funding, they need to write an article that’s gonna appeal to their audience too.”

Indeed, a study looking at cannabis’ effects on the retention of negative thoughts—“fading affect bias”—was recently written up in Live Science under the headline “Bad Vibes? Heavy Marijuana Users Hold on to Negative Feelings.”

Subjects were divided into users and non-users and then interviewed about their recent pleasant and unpleasant memories. The cannabis-using group was more likely to hang onto the bad ones and more likely to describe their memories in general terms, an effect also tied to depression known as “overgeneral autobiographical memory.”

Maddeningly, the study itself isn’t linked to in the piece and no mention is made of just who these people are. All we know is that one group smokes pot four or more times a week and the other doesn’t. Were the cannabis users also drinking a fifth of gin a day? Were they previously depressed? Did their dog just die?

Without answers to those questions, I have a hard time believing that it’s cannabis that caused their lingering negative emotions. And, of course, the study doesn’t claim causation, only correlation. 

While articles like this one are extremely frustrating, they’re not a blanket indictment of science. In the age of fake news and post-truth, science is more important than ever—it’s just important to verify it.

“It’s hard, in the world we live in where people don’t trust science anymore,” says Puccio. “If something looks fishy, look it up.”

And, she cautions, be wary of who’s delivering you your information.

“We have those fear-mongering establishment people saying, ‘It’s dangerous, it’s bad, we shouldn’t do it!’” she says. “And then on the other side, we have the cannabis activists who are like, ‘It’s the cure for everything! Nothing bad will ever happen! Everybody should smoke cannabis from the second they wake up until the moment they go to sleep, from birth until death.’ Neither of those is correct.”

To cut through the conflicting narratives, she suggests clicking through to cannabis studies that are cited and at least reading the abstract. It may seem like Greek, but it’ll give you an idea of who they studied, be it rats, veterans, or teenagers. It’ll also tell you how many subjects were included. If it was only four, the data doesn’t hold much weight. And it’ll usually mention what the researchers did or didn’t control for. Kaplan suggests that seeking placebo-based, double-blind trials can help too, as those are considered the gold standard of objectivity. Unfortunately, there’s hardly any cannabis studies investigating the therapeutic potential of the plant that are designed that way, because of the federal barriers to researching cannabis. 

But beyond evaluating the specific cannabis studies involved, it’s also a good idea to step back and just look at how the study in question is being applied to real life. In “Pot Holes,” for example, the main thrust of Grisel’s argument is that pot might be bad for teen brains and lots of teens are currently using pot so we shouldn’t legalize pot.

The thing is, exactly no one is suggesting that we give loaded bongs to kids in legal states. Kaplan agrees with cannabis studies that show negative impacts on brain development for teens, and also points out the potential triggering effect of cannabis on teens who are genetically predisposed to schizophrenia.

“I don’t think there are too many people out there advocating for adolescent THC use, unless it’s for severe medically relevant reasons,” he says.

There’s also the fact that every single legalization bill restricts the purchase of legal cannabis to adults 21 and older, and also includes increased funding for teen drug education. And while there’s an argument to be made that legalizing cannabis makes teens think it isn’t risky, that’s not exactly the message that the industry itself is trying to push. It is, however, a big part of the black market culture of cannabis. And, once more for the people in the back, dealers don’t check ID. Dispensaries do.

On top of all that, cannabis studies, in fact, suggests that teen use drops in legal states. Of course, that science is subject to the same scrutiny as any other study involving self-reported data on use but does come to us direct from the federal government. It seems strange that someone urging us to pay better attention to science would omit it.